Equations of Lines

# Equations of Lines - x-intercept The x-intercept is where...

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x -intercept The x -intercept is where the graph crosses the x axis. The word 'intercept' looks like the word 'intersect'. Think of it as where the graph intersects the x-axis . With that in mind, what value is y always going to be on the x -intercept? No matter where you are on the x- axis, y ’s value is 0 , that is a constant. We will use that bit of information to help us find the x -intercept. y -intercept If the x -intercept is where the graph crosses the x -axis where do you think the graph crosses for the y -intercept? If you said the y -axis, you are absolutely right. This time it is x ’s value that is 0 . Anywhere you would cross the y- axis, x ’s value is always 0. We will use this tidbit to help us find the y -intercept. Below is an illustration of a graph of a linear function which highlights the x and y intercepts: In the above illustration, the x -intercept is the point (2, 0) and the y -intercept is the point (0, 3).

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Keep in mind that the x- and y- intercepts are two separate points. There is only one point that can be both an x- and y- intercept at the same time, do you know what point that is? If you said the origin, (0, 0) , give yourself a pat on the back. Point/Slope Form of an Equation A line going through the point and having slope of m would have the equation We can use this form to plug into when we need to come up with a linear equation. When writing an equation of a line, keep in mind that you ALWAYS need two pieces of information when you go to write an equation: 1. ANY point on the line 2. Slope Once you have these two pieces of information, you plug the x and y values from your point and the slope ( m ) value into the point/slope formula. Slope/Intercept Equation of a Line
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## This note was uploaded on 02/18/2011 for the course MATH 101 taught by Professor Kindle during the Spring '11 term at South Texas College.

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Equations of Lines - x-intercept The x-intercept is where...

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